. The second temperature value is written for the 25 to 30% MC class; the third for the 20 to 25% MC class; and so on. In larger kilns, the heater may be needed in the latter part of the drying cycle. 3.24 solar-dehumidification drying kiln This lets the operator sort stacks by lumber species, so they will be easy to retrieve when the drying cycle is complete. The four charges of lumber ranged from 600 to 700 board feet (bf), and a woodworker with no dry-kiln experience operated the kiln. 8. A kiln schedule is a set of temperatures and humidities that are used during kiln operation. Matched to one of our L-Series and HT Dehumidifiers they can handle whichever species you are drying, fast drying softwoods to slow drying hardwoods. Adjust the baffles or fan direction to achieve good airflow. There are two ways to remove water from the DH unit, and they both work well. They are normally mounted in the gable of household attics, and they are designed to be used in high temperature environments. After two days operating only the fans and DH, I take note of the temperature. A higher humidity setting will run the unit sporadically to maintain that RH. My kiln schedule starts with running all fans and the dehumidifier for two days, measuring and removing water as it accumulates. I have sensors in the kiln for moisture levels & probes in the center of the wood attached to a lignomat moisture meter. hb```[@9p(T-3jO:g)@S 4Y]g7l\V!c!$Bf J B@&xcEz8PH@ZHs1/X$qOq,x'x$0.rWg*d XAT10 );9 With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. Kiln Drying . Should a Moulding Mill Bring Sawmill Operations In-House? My four main baffles consist of sheets of 1" Styrofoam insulation. The kiln operator sets the kiln controls based on the initial moisture of the lumber as it is loaded into the kiln. I usually see a large volume of water in the DH each night when I check the kiln. I know mixed loads are taboo, but this one worked well, other than the horse chestnut. Temps are in Celsius (20C = 70F, 40C = 105F). 0000002536 00000 n Also, for that approach to work, the chamber needs to be air tight. Basically, you dont want all of the air rushing out under the stack, so find a way to redirect it. 3.) Featuring lower cost drying at speeds equal to gas & steam, these kilns are continuously exceeding industry standards and changing the game. There are two main reasons for drying wood: Woodworking When wood is used as a construction material, whether as a structural support in a building . Dehumidification kilns are similar to other kilns in basic construction and drying times are usually comparable. Schedule for drying 4/4 and 5/4 upland red oak in a steam dry kiln. The T-bars are made from 1/2 galvanized pipe and are attached to the rafters with threaded pipe flanges. /Type /XObject I made a simple frame from plywood strips and attached the insulation sheets to them with screws and fender washers. Khmer Kiln: quite similar to the Anagama kiln however, traditional Khmer Kilns had a flat roof. Academia.edu no longer supports Internet Explorer. This makes lightweight baffles that can be easily moved and repositioned. Solar kiln drying was most effective in the summer and early fall, when kiln efficiencies were 90% to 67%, respectively, and drying times were 2 to 3/one-half/ times faster than air drying. A bead of silicone caulking between the subfloor and sill plate will prevent air infiltration. For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. This kicker board will help distribute the airflow more evenly through all layers of lumber. We proudly stand behind all of our products. A Checklist for Operators of Small Dry Kilns A companion to A Start-up Guide for Operators of Small Dry Kilns (FOR-132) Terry Conners, Forestry and Natural Resources Align the stickers over the starter blocks on the first course. A household dehumidifier (DH) removes moisture from the kiln chamber. Go to the first number designation (the temperature designation) and find the corresponding temperatures in the table below. A small electric heater supplies auxiliary heat to maintain adequate kiln temperature. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. Any small building could work, as long as it has a minimum of 2 x 4 framing, and will seal out unwanted air. stream This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. If you intend to kiln dry lumber from a green state, right off the sawmill, you will need to be well-versed in airflow rates and follow a detailed drying schedule. In the fourth column, write down the wet-bulb depressions (determined in #4 above), one for each Schedule Step, starting at the top (Schedule Step 1). Once the flooring deck is constructed, think about sealing the shed framing at every opportunity. There are two ways to remove water from the DH unit, and they both work well. Thicker lumber like 5/4 or quartersawn lumber is naturally more stable. Chinese, Korean or Japanese kilns have an arch roof. Check your local building codes for regionally specific requirements and electrical permits. Dr. Gene Wengert provides schedules for kiln drying hardwood lumber. Both restrained and control boards were dried to approximately 9 percent moisture content, representative of final in-service condi- tions. For single-stack kilns, stationary fans are adequate. My baffles hang from T-bar assemblies mounted to the ceiling. The conversion method described in the Dry Kiln Operator's Manual is not really accurate, but it is safe. Projects included design, construction, installation and commissioning of heat-pump based dehumidification equipment for seafood and fish gelatin products, hardwood lumber kilns and laboratory testing. Measure airflow over the stacks of lumber in various locations. A pre-hung steel exterior door is ideal in this situation, because it offers weatherstripping and is fully insulated. They are easy to use and give you precision control over your drying. hbbd``b` $ &UD\q@u Additionally, I have been underwhelmed by the performance of solar-operated fans. endstream endobj startxref The sheetrock also helps to protect the fiberglass insulation. I guess I am thinking that while I am seeing the wood's MC and the kiln's RH drop smoothly, the fact that the temperature jumps around a bit may mean that the drying rates are hard to control, hence my loss of horse chestnut. The second most common type of drying is called dehumidification drying. To browse Academia.edu and the wider internet faster and more securely, please take a few seconds toupgrade your browser. These kilns will typically hold several thousand board foot of lumber. The baffles direct airflow over and through the stack and prevent the top layers from drying too quickly. Attic fans are a perfect way to provide airflow over the stacks of lumber. The Bolivian wood products industry was surveyed to determine lumber drying capacity, technology and. Take the electronics out of the kiln, and continue operating the heater and fans during this phase. A 1.5-kW dehumidifier was installed in the solar dryer to determine the performance of a combined solar-dehumidification dryer. This report contains suggested dry kiln schedules for over 500 commercial woods, both temperate and tropical. 0 The kiln schedule information in the tables below has been assembled from many different sources, including drying texts and industrial contacts. 158 p. Dry kiln schedules for commercial woods : temperate and tropical. Wood poles subjected to a 22- to 34-day dehumidification kiln schedule with a heat treatment to 60C to the poles' core. Most species of hardwood lumber can be safely dried this way, once the moisture content is 20% to 25% or less. Measure airflow over the stacks of lumber in various locations. kiln/. Using a piece of paper with 6 columns, write down the Schedule Step numbers in the first column on the left. KD150 Series dehumidifier pdf manual download. More than 75 percent of the existing hardwood dry kilns in the United States are steam heated, are humidity controlled and have reversible fans inside the kiln. This slows the end-grain drying and limits the severity of end checking. This gives me a secondary method of tracking the drying process, using both water volume and moisture content (MC) readings. In the majority of cases, the drying schedules are from the world literature, with emphasis on U.S., Canadian, and British publications. In addition, weight on top of the stack can be helpful, but nothing replaces baffles for the best lumber yield. If required, look-up and write down the RH (sixth column) and EMC (seventh column) for each schedule step. Commercial scale steam kilns consume large amounts of energy. If the fans and dehumidifer generate enough heat to maintain a temperature of 100 to 120 F, then I wont use the auxiliary heater. As a result, the kiln schedules were too severe. For example, if you dry 7,500BF of fast drying Pine, you'd select the 8MBF chamber with the HT18 . The remaining width allows for a 36-wide door and space for your drying equipment. When properly loaded, this kiln can dry approximately 600 board feet of 4/4" lumber. Our approach was to build and operate a small dehumidification dry kiln. Typical . Additionally, a 12 air plenum is required between the walls and stacks of lumber. Kiln Systems. 1. a furnace or oven for burning, baking, or drying, especially one for calcining lime or firing pottery. Once the lumber is sterilized, it is ready for the conditioning phase. Drying small amounts of lumber using a dehumidification kiln is a suitable option for woodworkers even with limited knowledge of kilns. Would adding humidity at the start, bringing the initial relative humidity rate to 87% as suggested in the table, result in better product or faster drying? There may be more depression values than required; ignore the extra depression values in this table. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. In a professional DH kiln, the final climate for oak is 120F and <40>t over-dry it at that rate. The air flow rate through your stacks should be about 350FPM. A better choice might be a solar kiln, as you can dry wood from "wet" to 6-8 percent MC in 6-8 weeks. In smaller kilns, the heat generated by the fans and DH motor is sufficient to maintain temperatures in excess of 100 degrees. 0000006274 00000 n Dehumidification dry kilns operate at lower drying temperatures (typically below 150F) than do conventional kilns, which results in longer drying schedules. During the conditioning process, the only equipment operating are the fans, heater and the steam generator no dehumidifier. My number one priority was to build a kiln that was easy to load and easy to monitor. Manufacturer guarantees/warranties for power tools, CNC and laser products will supersede the Rockler Guarantee if these items are damaged or defective. For more capacity, consider a two stack kiln (12 x 12), or a three-stack kiln (12 x 16). Remote operation and networking is optional. If the temperature is below this range, I start the heater and adjust the thermostat accordingly. The common lumber name is used throughout. Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. If you dry 9,500BF of slower drying Oak, youd use the 10MBF chamber with the HT8 Dehumidifier. Enter the email address you signed up with and we'll email you a reset link. 2. (Dry Kiln Operator's Manual. My baffles hang from T-bar assemblies mounted to the ceiling. Job Opportunities and Woodworking Services, Dust Collection, Safety and Plant Operation, Air-Drying and Kiln-Drying Methods for Wide Plank Flooring, Drying lumber - selecting the best method. For the best experience on our site, be sure to turn on Javascript in your browser. This problem is magnified if the lumber is thin or flatsawn. USDA, 1991) . Y}-m+'@DQ4\h8GP]y@ yL. Apply foil tape to the edges of the main baffles to help protect the Styrofoam. I'm trying to find a timetable or drying schedule for the basic dehumidification kilns you see on youtube. A locked padlock Forum Responses If the fans and dehumidifer generate enough heat to maintain a temperature of 100 to 120 F, then I won't use the auxiliary heater. Corners where walls meet should be sealed with expanding foam sealant. I dont think the same could be said for an old reefer truck converted into a kiln (no matter how well it dries lumber). MC values in the kiln schedules are based on the wettest half of the kiln samples. The MC ranges are chosen so that the loss of the first one-third of moisture, and the highest risk of checking and staining, will occur in the first step listed.). This helps keep the lumber straight during the drying cycle; in fact, improper placement of stickers can permanently deform lumber. << Another reason I like the idea of a shed kiln is the flexibility of future use. BE CAREFUL--The first temperature value must be repeated for every MC class (column #2) that is above 30% MC. With a 130 F kiln temperature, sterilization will take 10 to 12 hours ( Dry Kiln Operators Manual, 1991 ). End baffles are also a good idea to prevent airflow from bypassing the stack entirely. I either use some cedar 3" x 5", or 4" x 4" stock. The column on the right I added part way through is the kiln's internal RH. Staggering the seams between the sheathing and siding layers helps avoid air infiltration. In larger kilns, the heater may be needed in the latter part of the drying cycle. Abstract. So, if you have 100 bf in the kiln, every 12 hours you would extract (12 hours *100bf * .0061 SDR) = 7.3 pints of water. Dehumidification: This kiln-drying process requires the use of a heat pump system to remove water from the wood. Insulation for walls and ceilings should be a minimum of R13. An official website of the United States government. Can also be used on any mobile device! Equalizing and Conditioning Many available kiln designs require a large, heavy door. A heavy-duty 1,500-watt space heater works fine. in the kiln to dry specific wood products at a satisfactory rate without causing objectionable drying defects. A shed kiln has minimal venting (usually one or two gable vents) and sealed soffits. Basically, you don't want all of the air rushing out under the stack, so find a way to redirect it. After seven to 10 days, I reverse the fan direction to make sure all stacks of lumber dry evenly. However, because wood from I hope that the sawyer coated the ends of the lumber with Anchor-Seal or oil-based paint when it was green. I like these starter blocks to raise the lumber a few inches off the floor. Nyle. Excel Program for Modeling Lumber Dry Kiln Operations - a model for lumber dry kiln operation. This helps keep the lumber straight during the drying cycle; in fact, improper placement of stickers can permanently deform lumber. At the planer mill, warped 2 by 4's represent a significant loss in value. If you intend to kiln dry lumber from a green state, right off the sawmill, you will need to be well-versed in airflow rates and follow a detailed drying schedule. 0000000591 00000 n 4.4 drying schedule moisture content drying schedule . The last step requires a short period of high humidity to relieve the drying stresses in the boards. After a short period of grumbling, they join me to lay down wood blocks for the first layer of lumber. This can be done by heating above 133F for 4 hours (measured at the core of the wood), or at 120F for about 7 - 10 days. Kiln dried wood typically sells for a third more than green lumber and eliminates the need for customers to incur costs associated with drying lumber . Once all the lumber is stacked and stickered, place baffles over the lumber. Difficult-to-dry species might not exceed 60 C (140 F). Dehumidification kilns from Nyle Systems in Brewer, Maine. I usually see a large volume of water in the DH each night when I check the kiln. How do I convert from the standard kiln schedules in the USDA's "Dry Kiln Schedules for Commercial Woods" and "Drying Hardwood Lumber" to an SDR-type schedule? Choosing a Kiln Schedule By. Sticker spacing can be increased to 24" apart for 5/4 or thicker hardwood. Drying lumber too quickly can lead to deep end checking, warping and case hardening. Formulating a Kiln Schedule Heres a classic project that both steps up and provides overflow seating. Taking moisture away at the rate the board will "safely" part with it . Select a heater with an adjustable thermostat and a tip-over shutoff. Your order will come with a return form with convenient instructions, or you may send your returns directly to Returns Department, Rockler Woodworking and Hardware, 4365 Willow Drive, Medina, MN 55340. There might be a problem with that if the chamber overheats and has to be vented because some water will leave that way. A heavy-duty 1,500-watt space heater works fine. Corrosion resistant epoxy coated aluminum cabinets and specially coated dehumidification coils for an extra long life. endstream endobj 283 0 obj <>/Metadata 40 0 R/OCProperties<>/OCGs[294 0 R]>>/Outlines 53 0 R/PageLayout/SinglePage/Pages 280 0 R/StructTreeRoot 72 0 R/Type/Catalog>> endobj 284 0 obj <>/Font<>/Properties<>/XObject<>>>/Rotate 0/StructParents 0/Tabs/S/Type/Page>> endobj 285 0 obj <>stream )f7haRoMRhib5Sd|-=RBkBBN r-hzf+1\IFgk;v]3_, KxL$9oL "Qw#"BFGfk}>cT2g yP K|7@N*v9!Wy9jB. op(y"X)Fz"q]fQC/ha>7=k_p}}^VXQmj e'2fyXQ{~23X^H1,d>Hq|^KQ*cN=yF%z. Consider not only the space for the lumber stacks, but extra floor space to easily load and monitor the charge of lumber. In this research, a drying restraint system was evaluated as a means of warp reduction in 8- and 16-foot-long SYP lumber. It can be constructed in any style, with architectural features that match or complement an existing home. 6. I am also curious why an initial temperature of 90F would have been selected. With advances in spray foam insulation, it may be possible to seal older, drafty structures as well. Looking at the cost-benefit analysis of a shed kiln can be enlightening. 0000004213 00000 n The thinner the stock, the more critical sticker placement becomes. Not bragging or anything! Wood-Mizer dehumidification and solar wood kilns range from 300 to 35,000 board feet capacity for drying lumber. Determine the equalization settings and conditioning settings, as required. Different species should not be loaded simultaneously into the kiln due to often differing kiln schedules. That purchase was an average deal, and one I dont consider a particular bargain. Soon the DH won't show much water collected in the tray. For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. After four days, I decrease the RH setting on the DH to 30% and continue to run the fans. What can you do to speed up drying time? Kiln drying is the process of drying wood in a controlled environment, where temperature, air circulation and humidity are monitored and stabilized. Kiln drying lumber is a simple, cost effective method recommended for anyone who wants to increase profits by selling dried lumber. 293 0 obj <>/Filter/FlateDecode/ID[<87A322ACC143C740A97F712BC6C2FBCD>]/Index[282 20]/Info 281 0 R/Length 68/Prev 378162/Root 283 0 R/Size 302/Type/XRef/W[1 2 1]>>stream The baffles do not need insulating properties, and plywood would work just as well. Kiln drying normally involves temperatures in the range of 40-75 C (about 100-170 F). By setting the relative humidity (RH) on the dehumidifier, you can control how often it runs. I like these "starter blocks" to raise the lumber a few inches off the floor. Milling the stickers square is advantageous over a rectangular cross-section, because no matter how you place the stickers they will form a level stack. Initially, I set the DH to 40% RH, because I dont want to remove moisture too quickly. This prevents dead spots inside the chamber that experience limited airflow. John Baines Reply to Dann Barry 1 year ago I use a Rockler steam generator, item #42826 (www.rockler.com). Without baffles, the top layers of lumber experience "potato chipping" with cupping, twisting or warping. This returns some moisture to the very dry exterior of the lumber, while not affecting the core moisture level. 4. Also check that air isnt escaping around the side baffles or under the stack of lumber. To hang the baffles, simply attach hooks to the plywood frame. Air speed of 350 feet per minute is appropriate for common hardwoods such as oak and maple. 0000006297 00000 n 906 0 obj << /Linearized 1 /O 908 /H [ 710 498 ] /L 501020 /E 6532 /N 45 /T 482781 >> endobj xref 906 12 0000000016 00000 n I then manually rotate the fan boxes halfway through the drying cycle. ) or https:// means youve safely connected to the .gov website. The velocity through the load is assumed to be between 275 and 350 fpm, except for the white woods (including maple, ash, basswood, hackberry) where higher velocities (up to 600 fpm) are desired and acceptable. The schedules can also be formulated manually as follows. Always avoid conditions that add moisture back to the lumber, especially during start-up. An anemometer confirms that your effort constructing baffles was worthwhile. We are proud of the quality of our products, and we stand behind them 100%. Take a moisture reading in the end grain with a pin-type moisture meter or remote probe. Installing sheetrock and fire taping is a good idea for a heated room. For all kiln drying schedules, a heater should be used to sterilize the lumber and kill any insects that may be present. 6 0 obj Total costs for the materials were $2,704 based on 2006 prices. The thinner the stock, the more critical sticker placement becomes. txN.a!HQ)FmCw~{B1Aq_!+zN#+j For a kiln temperature of 140 F, sterilization takes three to five hours. This shed will be essentially unheated for much of the year and very hot during the kiln-drying cycles. Instead of using expensive electrically reversible fans designed for commercial kilns, I came up with a simple hardware solution. This is because it needs to be dried to a lower moisture content than wood will air dry to outdoors. Our next kiln charge is scheduled to begin around February 6, 2023. Be sure that all of the kiln equipment is working prop-erly before lumber is loaded into the kiln. For a small scale shed kiln, I recommend a maximum footprint of 200 square feet. I am using a household . 0000002827 00000 n squares, handle stock, gunstock blanks) are given for many species. With a 130 F kiln temperature, sterilization will take 10 to 12 hours (Dry Kiln Operators Manual, 1991). Instead of using expensive electrically reversible fans designed for commercial kilns, I came up with a simple hardware solution. Make sure the total amp draw is well within the limit of your electrical circuit. However, if you kiln dry hardwood lumber that has already been air dried, the process is much more forgiving. Evaluation of kiln-drying schedules for wild cherry wood (Cerasus avium), Model to assess energy consumption in industrial lumber kilns, Mathematical modelling and experimental investigation of dehumidifier drying of radiata pine timber, A survey of Bolivian lumber drying operations, Warp reduction of SYP lumber by restrained drying, Western Juniper Drying Project Summaries, 1993-96, Vacuum contact drying kinetics of Jack pine wood and its influence on mechanical properties: industrial applications, Kiln drying behavior of lumber from ten fast-growth plantation species in Costa Rica, Effect of fire-retardant treatment and redrying on the mechanical properties of Douglas-fir and aspen plywood, Properties of Douglas-Fir and Aspen Plywood, A numerical study on the influence of the bond-line diffusivity on moisture-related stresses and deformations of three-layered spruce cross-laminates, Error in Estimates of the Moisture Content of White Oak Kiln Sample Boards, Green Kerfing Treatment for Improving Softwood Lumber Drying: A Review, A comparison of kiln-drying schedules and quality outcomes for 4/4-thickness black cherry lumber sawn from small-diameter logs, A comparison of kiln-drying schedules and quality outcomes in 4/4-thickness black cherry lumber sawn from small-diameter logs, Data bank for short-length red oak lumber, Hardwood lumber widths and grades used by the furniture and cabinet industries: Results of a 14-mill survey, Lumber and veneer recovery from intensively managed young-growth Douglas-fir, WOOD-FRAME HOUSE CONSTRUCTION U.S. DEPARTMENT OF AGRICULTURE FOREST SERVICBAGRICULTURE HANDBOOK NO. High Temperature Kiln Drying Systems (160F) Loads up to 350,000 BF; Pull up to 20,000 pounds of water daily; Use standard drying schedule; Precision temperature and RH . This air space is absolutely critical for even airflow, so count on the extra floor space right from the design phase. A dehumidification kiln makes sense particularly when the lumber is air-dried first. If MC readings still arent at the desired range, the heat may need to be increased for the remainder of the drying cycle. This problem is magnified if the lumber is thin or flatsawn. I cannot stress the importance of baffles enough. These well-known dehumidification kiln packages have been among our bestselling products for the past 30 years. For a single-stack kiln I recommend a minimum shed size of 8 x 12. If your lumber stack is built on starter blocks, you will need to limit airflow there as well. Reweigh and obtain the oven dry weight. A shed kiln is an attractive alternative for a couple of reasons. After four days, I decrease the RH setting on the DH to 30% and continue to run the fans. If MC readings still arent at the desired range, the heat may need to be increased for the remainder of the drying cycle. I was hoping someone could point me in the right direction or share experience. You could use the dehumidifier to dry wood but it would not be part of a "kiln." Just be a different process. Loading the kiln begins by rousing my sons and letting them know Ive planned a day of work. Equalizing and conditioning are required for almost all hardwood lumber. This can create internal stress in the lumber that is released when sawing. When the operating conditions of this option are followed the material will meet the requirements of being kiln dried (KD) and heat treated . For the sterilization phase, air temperature needs to be around 140 F, for three to five hours. Case hardening is a defect caused by the outer portion of a board drying quickly, while the inner portion dries more slowly. In this system, moist air is not vented out of the kiln but is dehumidified, then recirculated . HT systems use 40-60% less energy than gas-fired or steam dry kilns. With each load I did not have the initial relative humidity rate. 3, a simplified transverse section of a kiln chamber with an energy recovery and dehumidification system is shown. My kiln uses four ceiling-mounted fans, each rated for 1,600 CFM. Ignoring for a moment the merits of a homebrew DH kiln versus a Nyle, I was curious to see that rather than referencing the standard kiln schedules (e.g. For a kiln temperature of 140 F, sterilization takes three to five hours. Difficult-to-dry species might not exceed 140 degrees F. Dehumidification kilns are very . In the third column, write down the appropriate dry-bulb temperatures. Schedules for several thicknesses and specialty products (e.g. At the end of the cycle I have the opposite problem. For single-stack kilns, stationary fans are adequate. They are based on different air flow rates, etc. A lower RH setting will call for the DH to run more often. Once all the lumber is stacked and stickered, place baffles over the lumber. Kiln dried wood typically sells for a third more than green lumber and eliminates the need for .